Read the information below about meiosis and then try these exam questions.
Meiosis achieves this reduction in chromosome number by having two rounds of cell division rather than one round as seen in mitosis (the type of cell division that happens in 99% of your cells).
Why have such a complicated process? Why don’t all cells divide by mitosis? Well, meiosis introduces a little bit of variation into a population at every cell division. This is important because variation is the raw material that natural selection works on.
Without variation there would be little in the way of evolutions and species would be susceptible to extinction is something in their environment changed.
Remember: meisis has two ways of producing variation. The first is independant assortment of chromosomes. The diagram below shows two equally possible arrangements of these two homologous pairs of chromosomes.
The other way that meiosis introduces variation is through crossing over. Here is what we learnt about in the lesson:
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